Feathered propeller control



Feb. 23, 1965 Filed .June 24, 1965 FIGA l.. L. GAuBls x-:r Ai. 3,170,521

mvEN-roas LEONARD 1 @Ausls EDWARD H- KUSIAK ATTORNEY Feb 23 1965 l.. l.. GAuBls ETAL FEATHERED PROPELLER CONTROL 2 Sheets-Sheet 2 Filed June 24, 1963 ATTORNEY l 3,170,521 v FEATHERED PRPELLERv CQNTROL Leonard L. Gaubis, East Granby, Conn., and Edward H.

Kusiak, Springfield, Mass., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware z Filed June 24, 1963, Ser. No. 289,844 3 Claims. (Cl. Utl-160.29)

This invention relates to aeronautical propellers hav- United States Patent O ing lvariable pitch propeller blades and adapted to be moved to a feathering; position and particularly to means for preventing the propeller fromrotating when in the feathered position.

It is an object of this invention to provide means Ain la variable pitch propeller` for preventing the propeller a propeller as described a purely mechanical system for automatically and continuously seeking zero r.p.m. of a feathered propeller.

A still further object of this invention is to provide in a variable pitch propeller as described means for rotating the propeller blades about their longitudinal axis While in a feathered position in order to obtain a blade angle to prevent the propeller from rotating about its rotating axis. y

It still is a further object of this invention to provide a self-seeking zero r.p.m. feather angle in a variable pitch propeller blade by the use of a mechanism which is characterized as being relatively simple to manufacture, economical andcapable of rugged use.

Other features and advantagesrwill be apparent from 'the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

FIG. 1 'is a schematic illustrating a variabley pitch propeller blade and its control mechanism to which this invention has been utilized.

`FIG. 2 is an isometric and partial sectional view illustrating the invention.

Variable pitch propellers capable of being placedin a feathered position are generally well known in the art and as equally well known ideally, the feathered position is that position which offers the least resistance tothe air-stream during flight of the aircraft. When the blades are placed in the feathered position, it is customary to hold a fixed blade angle by braking mechanism of the hydraulic or mechanical type which prevents the propeller blade from seeking a lower propeller angle. However, as is well known, the feathered angle selected is generally unsatisfactory because some rotation about the propeller axis will be evidenced. This rotational movement, known in the art as windmilling, imposes a considerable amount of drag to the aircraft impeding its ight, as well as imposing loads on the engine. This is particularly a critical problem in propeller installations driven by turbo-types of power plants. Hence, it is desirable and in some installations absolutely necessary to provide means for preventing the propeller from rotating about its rotational axis; i.e., preventing windmilling. Obviously, when the propeller is placed in the feathered condition, any power derived as a result of the rotation of the propeller is automatically cut off. We have found that lby employing this invention to a variable pitch propeller no external power is necessary for automatically adjusting the blade angle in a position to seek zero rotation of the propeller.

In certain installations the propeller incorporates mechanical feedback means for feeding back the blade angle to a servo control unit. If such a system is utilized,

it is possible to modify the existing feedback system rice and mechanism in order to achieve the zero rotation. While the invention rwill be described in connection with a propeller that incorporates this type of feedback mechanism described above, it is to be understood that the invention is not limited thereto, 'l

Now referring tro-FIG. l which shows this invention in its preferred form showing a propellerv generally indicated by numeral 10 as having a pluralitykof propeller blades circumferentially mounted in hub 14 in a ywellknown manner. The propeller contains a. dome as- Yse'rnblyv 16 which surrounds a pitch changing piston 1S operatively connecting the pitch changing cam mechanism 2t) rotably mounted therein. Bevel gear 22 is mounted on one end of cam 20 and rotates therewith and engages a bevel gear 24 carried on the root of the blade 12. As shown in the drawing, enginev 26 is coupled to the propeller 10 by any suitable means generally illustrated by numeral 28 for rotating the propeller and obviously 'the propeller blades carried therewith about the propeller center line. l

In order to rotate the propeller about its longitudinal axis or change pitch, pitch changing piston 18 responds tothe .position of distributor valve 30 by virtue of delivering pressurized Huid to either side of pitch changing piston 18 through the fluid conducting lines 32 and'34. The pressurized iluid issuing from pump 36 to line 38 and into the distributor -valve is directed to the fore or aft end of piston 18 by virtue of movement of the spool 40 of distributor valve 30. For example, when the spool is moved to the left, high pressure fluid discharging` from line 38 communicates with line 32'for directing high pressure fluid into chamber 42 located in the dome. This urges the piston, to move to the kright 4for rotating the blade 12 about its longitudinal axis. Of course, the rotational movementis obtained by the use of cam 20 and the attendant bevel gears 22 and 24. Simultaneously, the uid evidenced in chamber 44 located on the aft side of piston 18 communicates with drain via line 34 through distributor valve 30 and line .46.,

In order to rotate the propeller blade in the opposite direction spool 40 is positioned to the right for directing high pressure fluid from pump 36 into 1ine134 and ultimately into chamber 44 to act on the aft end of piston 18 for moving the same to the left to cause the rotational movement of cam 20 vfor varying the pitch of blade 12. Simultaneously, when spool 40 is at the right position, it is obvious from an inspection of the drawing that fluid in chamber 42 will be directed to drain through distribu, tor valve 30 via lines 32 and 48 and returned back to the reservoir 50.l l p Controls for variable pitch propellers are Well known in the art and basically, the control serves to maintain the propeller r.p.m. at a constant value. This is accomplished by sensing the r.p.m. of the propeller by a speed responsive device and comparing that speed with a preselected value. The control holds the speed at that value by changing the pitch of the propeller blade 4in response to any error created by the speed responsive device. Devices such as this are well known in the art and'for more detail to such devices reference is hereby made to Patent No. 2,664,960, granted to M. E. Longfellow et al., on January 5, 1954, and Patent No; 2,850,103, granted to D. R. Pearl, on September 2, 1958. Still referring to FIG. 1, the control system for maintaining the r.p.m. of the propeller lat a constant value is shownnas basically comprising a suitable speed governor 60 which senses the speed of .the engine and the position of the pilot lever 62 and comparing both signals for controlling the position of governor pilot valve 64. Pilot valve 64 comprises `spool element 66 having a pair of lands 68 and 7tl cooperating with ports 72 and 74 respecaft chambers in servo motor- 78-to drain.l When the rpilot valve 64 isxmoved downwardly, highpressure de veloped7 by pump 80 is directed through line 82 to line 84 i tively for directing high jn'essure to either side of piston V76 of servo motor 78, asl wellUasfconnecting the 'fore ,or

n turn, imparts rotational movementtogears 112and11tl.

vSince gear 110 is attached Ito-the y'feedback shaft :163, 1t

and into the lower chamber 86 of fthelservov motor 73' and "simultaneously, land 64 uncovers line 8S which Vcommunicates Withfluid in chamber 91). for directing the fluid in chamber 91) to drain through lines92 and'94 and even- Vtually to the reservoir 916. Sirnilarlygif the pilot valve 4i'smoved upwardly, ports 72 and 74 are uncovered sc as to [direct high pressure fluid from discharging from line l arrangement cause bevel, gear 2e to rotate and hence. l

rotate blade V12 vabout its longitudinal axisV 1nv a direction,

8.2 to chamber 9i) via line 83 and directing fluid evidenced in'chainber 85 to'drain via lines S4 and 9d. f e

l The ultimate effect is thatpiston 76 ismoved 1n either upward or downward direction and attached rack gear 'U98 is moved to rotate pinion gear 11m. The pinion, gear is 'attached to a shaft 1tl2rwhich engages a suitable spline mechanism 104. The splineV mechanism serves'to translate the spool40` of distributor valve 30. K From the foregoing itis apparent `that movement of piston 76 will cause spool 40 to direct'tluidy tothe dome ofi-.the propeller for elfectuating a pitch change movement; Thus, if'an increase of` speedris evidenced by the governor 60, the control Wil-l respond to the speed error for effectuating "a pitch change movement to reduce they error for maintaining the rpm. of the propeller at the speed dictated by the position of pilot lever r62.

Feedback is'achieved'by incorporating a feedback shaft 1&8 extending'coaxially about the propeller center line which has the cam 2d and carries at its aft end spur gear ever, a change in attitude, angle of `attack-of the air- `str'eam,"`drag ortheylike causes the propellerlto rotate, gear 114 will `rotate relative to fixed gear 14@ which, in

will cause rotational movement of *bevel gear 22 relative tothe rpm. of the.propeller.y The rincrementqinthe f Speed overv the propeller speed causeclgbyV the gearing to return thepropeller'tofa zero rpm; condition.;

kNow referring to FIG.`2 which' shows in rmore detail a propeller utilizing thisinventiont'as comprising-a dome assembly 202 fand ahhh v'assembly Zilli. Ak pluralityy of` blades 20.6 are circumferentially supported'in the` hub about the propeller blade axis. The bevel gear 20S 1s Y'mounted' on the-root 'of blade-206 ,and engagesfbevel gear 211i carried by. feedback shaft 212. Mountedon the opposite end ofvfeedback shaftn212, which shaft is coaxially mounted about the center line, of the propeller axis,

, is gear 21,4. Gear 214, in turn, engages l'gear' 216 which,

;v The .spur gear engages another spur gear 112 Y which, in turn, engages gear 114 andv this gear train serves to drive the, differential gearing 116. Ring gear118 contains internal teeth Whirchrengage the Ateeth of gear v 114, and external gears 122 which engage the differential gear 124. for driving the'diierential.V As shown' in the drawing, the other input to the differential is through gear 126 driven by the propeller by virtue of the gear 128 attached to the hub extension 13.1). As the operation of 'the dierential gearing isnot necessaryto ancxplanation of this invention, lit is only pointed out for convenience that the differential gearing, in turn, drives thegear 132` which is attached tothe spline member-.164 for repositioning spool 40. Hence, bythe diiferentilal `and the feedback connecting members, the position of the propellet' blade-is relayed back to the control system so that the'lands of spool'valve itl will be on line-on-line position with its cooperating yports in distributor valve 30,V

` whenever an equilibrium or steady-state condition exists `In accordance .with this invention we `provide means f for preventing the vpropeller from windmilling byy assuring that the blade will seeka zero rpm. pcsition when the propeller blade is `placed inits'lfeathered position. flo accomplish this we provide spurgear 16.0 which .engages a set of teeth formed on member 11S. Gear is supported by shaft 142 which extends into the braking mechanism 144. Braking mechanism'144 may be of any suitable type *of brake such as a friction brake which responds to the position of lever 146 by action of its connecting linkages 143 .and 150. When lever 146 is pivoted about pivot point 152, the brake will be engaged.- for prcventingshaft 142 and ultimately gear 146 from rotating. This will lock ring gear member 118 into place and prevent it from rotating while allowing gears 114,112, 110, bevel gears`22. and 24 to rotate.

The operation of the selfseeking zero r.p.m. mechanism will now be described. Assume that the propeller hasbeen'placetd in the feathered condition and that the brake 144 is energized. When the propeller has reached the true feathered position, the blades' will be rotated such that the leading edge is parallel to the airstream Y and offers the least resistance thereto and no rotational movement of the propeller will be evidence. If, how-` in turn, engages gear 21S which, in turn, engages the internal tteeth of ring gear22i. Ringy gearv 226 carries a yset of external'rgears which engage spur gear A224 mounted onfshaft 226.V Shaft 22e connects to braking mechanism 228 which may carryf a suitable braking ,shoe 239V and cooperating friction member 232. Engagement of the brake may beeifectednin any suitable manner and i is y:not important .to` van explanation of this invention.

As was explained in connection with FIG. 1, when Vthe Ypropeller is placed in the feathered condition, the invention serves to automatically and continuously seekV azero rpm. of the propeller. operation is as follows: v i

Y (l) While in che nonfeather'ed 'condition` the brake is disengaged` until feathering operation isrinitiated to cause the vblade to move to,itsfeatheredposition to an angle;

is occasioned-by overfeathering the propeller'as was men- Y tioned in the step above.v v(4) Sincegear 216 is turning `clockwise (looking aft) about its axis, it will cause the v feedback vshaft 212 to turn counterclockwise. The gear mesh between bevel gear 210 and 208v causes the blade to Vdecrease'angle luntil zero rotation about thel propeller rof n tational. axis occurs.

l (K5) A change in iiight attitudevor a speedV requiring a higher feathered angle wouldcause clockwise windmilling about the rotational axis and a `di-y rection of rotation for gears 218, 216, etc. would be `the reverse of those describedl immediately above. The blade angle will then increase until zero rotationoccurs. (6) When it is desirable to unfeather, the feather brake is released allowing the feedback mechanism to function in its normal operating condition. l A,

What has been shown by this invention is a simplified Y means characterized asV being a positive method of seeking zero rotational speed when the propeller has been placed in a feathered condition. Since it is customary to provide feedbackmechanisrns to certain propeller instalf lations, it is a simple'expedient to modify such feedback mechanism to accomplish zero rotation byjincorporation `of this invention.

It is tobe understood that the inventionis notlimitedy to the specific embodiment` herein illustrated and Vdescribed,.b,ut maybe used in other ways Without Vdeparting from its spirit as defined by the following claims.

We claim: i

1. Fora variable pitch propeller having a plurality of blades movable to a feathered position, a4 hub supporting sa1d blades, means in said hub for` automatically main-` Preferably, the sequence-'of Vini. .l

` blades are in a feathered position, said means responsive to rotational movement of said propeller for adjusting the pitch of the blade to either a higher `or lower blade angle to prevent said rotational movement.

2. Fora variable pitch propeller having a plurality of blades movable to a feathered position, mechanical means for automatically adjusting the pitch of the blades to the feather position and keeping the propeller in a nonrotational position by adjusting the pitch in a decrease or increase angular position when said blades are in the feathered position, said mechanical means comprising a shaft mounted coaxially with the rotational axis of the propeller, a rst gear carried by said shaft and a second gear spaced from said rst gear also carried on said shaft, said first and second gears being rotatable with said shaft, a gear carried on the end of the'blades engaging said rst gear, a lirst spur gear engaging said second gear, a second spur gear engaging said rst spur gear, a ring gear engagn ing said second spur gear and braking means retarding ferentially supported around said hub, an elongated shaft in said hub extending along the axis of rotation of said propeller, a rst gear carried on the root of each of said blades extending in said hub, a second gear carried on the end of said shaft engaging said first gear for causing said References Cited by the Examiner UNITED STATES PATENTS 2,108,660 2/38 `Farrell 170-160.29 X 2,664,960' 1/54 Longfellow et al. l70-160.2 2,850,103 9/58 Pearl l70-135.7 3,068,943 12/62 Fischer 1704-1602 JULIUS E. WEST, Primm Examiner. 

1. FOR A VARIABLE PITCH PROPELLER HAVING A PLURALITY OF BLADES MOVABLE TO A FEATHERED POSITION, A HUB SUPPORTING SAID BLADES, MEANS IN SAID HUB FOR AUTOMATICALLY MAINTAINING THE PROPELLER IN A NONROTATIONAL POSITION WHEN THE BLADES ARE IN A FEATHERED POSITION, SAID MEANS RESPONSIVE TO ROTATION MOVEMENT OF SAID PROPELLER FOR ADJUSTING THE PITCH OF THE BLADE TO EITHER A HIGHER OR LOWER BLADE ANGLE TO PREVENT SAID ROTATIONAL MOVEMENT. 